Quickly adding new columns to tables in Denali

In short, it will be possible to quickly add a new non-nullable column to a table. This operation is quick because it is a metadata change. Prior to this new feature, it would be necessary to wait until the server physically manipulates every row in the table. This manipulation would involve exclusive table locking. It would possibly include splitting pages and lots of disk I/O.

This feature would be an absolute boon in a 24x7 system and it should be handy for avoiding lengthy schema upgrades on any system with large tables.